gallery:
dif2 matrix:
[[ 2. -1.  0.  0.  0.]
 [-1.  2. -1.  0.  0.]
 [ 0. -1.  2. -1.  0.]
 [ 0.  0. -1.  2. -1.]
 [ 0.  0.  0. -1.  2.]]
frank matrix:
[[5. 4. 3. 2. 1.]
 [4. 4. 3. 2. 1.]
 [0. 3. 3. 2. 1.]
 [0. 0. 2. 2. 1.]
 [0. 0. 0. 1. 1.]]
helmert matrix:
[[ 0.4472136   0.4472136   0.4472136   0.4472136   0.4472136 ]
 [ 0.70710678 -0.70710678  0.          0.          0.        ]
 [ 0.40824829  0.40824829 -0.81649658  0.          0.        ]
 [ 0.28867513  0.28867513  0.28867513 -0.8660254   0.        ]
 [ 0.2236068   0.2236068   0.2236068   0.2236068  -0.89442719]]
moler3 matrix:
[[ 1. -1. -1. -1. -1.]
 [-1.  2.  0.  0.  0.]
 [-1.  0.  3.  1.  1.]
 [-1.  0.  1.  4.  2.]
 [-1.  0.  1.  2.  5.]]